Toby Betts
Public domain.

Like any other piece of software (and information generally), this
patch comes with NO WARRANTY.

--- Overview ---

TempleOS includes a very basic FAT32 kernel driver. While the FAT32 file
system adds backwards-compatible support for long file names (LFNs)
allowing a file name to contain up to 255 characters, the TempleOS FAT32
driver only allows at most 26 characters. This patch edits the default
TempleOS FAT32 kernel driver to extend the maximum permitted file name
length to 39 characters, which *includes the '\0' null byte* at the end
of the file name's C string array.

--- What This Patch Does ---

The TempleOS FAT32 implementation is very minimal and I find patching it
to be incredibly finicky. In order to add one additional LFN record to a
file on FAT32 in TempleOS requires (1) making changes to the maximum
permitted file name length in the TempleOS kernel, (2) disabling all
support for the preferred RedSea TempleOS file system, and (3) carefully
extending the "fat_long_name_map" logic in /Kernel/BlkDev/FileSysFAT.HC
to handle files with names between 26 and 39 characters.

--- Installation ---

This is a standard patch-format file and uses the common UNIX/Linux
patch(1) utility. Copy this file to an installed TempleOS host -- a
shared-partition, dual-boot setup is recommended, see Notes for details
-- and run the following commands. Assuming the TempleOS partition is
"/dev/sda1":

1. Mount the TempleOS partition from UNIX or Linux:

  mount -o noatime /dev/sda1 /mnt/sda1
  cd /mnt/sda1

2. Check that the patch will apply cleanly without making any changes to
your system:

  patch -p1 --dry-run < /path/to/patch

Confirm that no patch hunks report as failing or would be rejected. Do
not continue without correcting all errors. If the patch applies
cleanly, proceed to the next step.

3. Run the patch utility to apply the changes:

  patch -p1 < /path/to/calm.patch

4. Boot TempleOS and make a backup of your existing kernel:

  Copy("/Kernel.BIN.C","/Kernel.BIN.BAK");

5. Compile a new kernel to accept the changes made to the kernel header
file. Follow the interactive kernel compiling process:

  BootHDIns;

6. Repair your bootloader (as needed).

--- Notes ---

Related information you might find useful:

  - Shared-partition, dual-boot TempleOS setup: "The Cathedral and the
    Bizarre, or Dual-Booting for Fun and Prophet"
    <URL:https://su.bze.ro/talks.html>

--- Version History ---

2025-03-03, v.1.0 - initial release


--- old/Kernel/BlkDev/FileSysFAT.HC
+++ new/Kernel/BlkDev/FileSysFAT.HC
@@ -184,6 +184,8 @@
   offset(CFAT32DirEntryLong.name3)+2
 };
 
+#define FAT32_VFAT_LEN 13
+
 Bool DirLongNameFill(CDirEntry *tmpde,CFAT32DirEntryLong *de,I64 *xsum)
 {
   I64 i;
@@ -198,13 +200,18 @@
   }
   switch (de->ord&0x3F) {
     case 1:
-      for (i=0;i<13;i++)
+      for (i=0;i<FAT32_VFAT_LEN;i++)
 	if (!(tmpde->name[i]=ptr[fat_long_name_map[i]]))
 	  return TRUE;
       break;
     case 2:
-      for (i=0;i<12;i++)
-	if (!(tmpde->name[i+13]=ptr[fat_long_name_map[i]]))
+      for (i=0;i<FAT32_VFAT_LEN;i++)
+	if (!(tmpde->name[i+FAT32_VFAT_LEN]=ptr[fat_long_name_map[i]]))
+	  return TRUE;
+      break;
+    case 3:
+      for (i=0;i<FAT32_VFAT_LEN;i++)
+	if (!(tmpde->name[i+2*FAT32_VFAT_LEN]=ptr[fat_long_name_map[i]]))
 	  return TRUE;
       break;
   }
@@ -240,21 +247,38 @@
   if (StrCmp(dname,tmpde->name)) {
     ord=0x41;
     xsum=FATNameXSum(de->name);
-    if ((l=StrLen(tmpde->name))>13) {
+    l=StrLen(tmpde->name);
+    if (l>2*FAT32_VFAT_LEN) {
+      ptr=&ld[de_cnt];
+      MemSet(ptr,0,sizeof(CFAT32DirEntryLong));
+      ld[de_cnt].attr=RS_ATTR_LONG_NAME;
+      ld[de_cnt].xsum=xsum;
+      ld[de_cnt].ord=0x43;
+      for (i=2*FAT32_VFAT_LEN;i<l;i++)
+	ptr[fat_long_name_map[i-2*FAT32_VFAT_LEN]]=tmpde->name[i];
+      i++;
+      for (;i<3*FAT32_VFAT_LEN;i++)
+	ptr[fat_long_name_map[i-2*FAT32_VFAT_LEN]](U16)=0xFFFF;
+      ord=1;
+      l=2*FAT32_VFAT_LEN;
+      de_cnt++;
+    }
+    if (l>FAT32_VFAT_LEN) {
       ptr=&ld[de_cnt];
       MemSet(ptr,0,sizeof(CFAT32DirEntryLong));
       ld[de_cnt].attr=RS_ATTR_LONG_NAME;
       ld[de_cnt].xsum=xsum;
-      ld[de_cnt].ord=0x42;
-      for (i=13;i<l;i++)
-	ptr[fat_long_name_map[i-13]]=tmpde->name[i];
+      ld[de_cnt].ord=1+ord;
+      for (i=FAT32_VFAT_LEN;i<l;i++)
+	ptr[fat_long_name_map[i-FAT32_VFAT_LEN]]=tmpde->name[i];
       i++;
-      for (;i<26;i++)
-	ptr[fat_long_name_map[i-13]](U16)=0xFFFF;
+      for (;i<2*FAT32_VFAT_LEN;i++)
+	ptr[fat_long_name_map[i-FAT32_VFAT_LEN]](U16)=0xFFFF;
       ord=1;
-      l=13;
+      l=FAT32_VFAT_LEN;
       de_cnt++;
     }
+
     ptr=&de[de_cnt];
     MemSet(ptr,0,sizeof(CFAT32DirEntryLong));
     ld[de_cnt].attr=RS_ATTR_LONG_NAME;
@@ -263,7 +287,7 @@
     for (i=0;i<l;i++)
       ptr[fat_long_name_map[i]]=tmpde->name[i];
     i++;
-    for (;i<13;i++)
+    for (;i<FAT32_VFAT_LEN;i++)
       ptr[fat_long_name_map[i]](U16)=0xFFFF;
     de_cnt++;
     MemSet(&de[de_cnt],0,sizeof(CFAT32DirEntry));
@@ -562,13 +586,17 @@
 Bool FAT32DirNew(CDrv *dv,U8 *cur_dir,CDirEntry *tmpde,Bool free_old_chain)
 {
 //See $LK,"::/Doc/CutCorners.DD"$.
-  CFAT32DirEntry *buf,*last_buf,*tmp_buf,de[3];
+  CFAT32DirEntry *buf,*last_buf,*tmp_buf,de[4];
   I64 i,attr,avail_cnt,de_cnt,c,
 	cur_dir_entry,entries_per_clus,
 	cur_dir_clus,xsum=0,last_dir_clus=INVALID_CLUS;
   U8 ch;
   Bool written=FALSE,unlock,unlock_break;
   CDirEntry long_name;
+  if (CDIR_FILENAME_LEN<StrLen(tmpde->name)) {
+    PrintErr("Invalid File Length: \"%d\".\n",StrLen(tmpde->name));
+    return FALSE;
+  }
   FAT32DirFill(&de,tmpde,&de_cnt,dv->fat32_local_time_offset);
   MemSet(&long_name,0,sizeof(CDirEntry));
   try {

--- old/Kernel/BlkDev/FileSysRedSea.HC
+++ new/Kernel/BlkDev/FileSysRedSea.HC
@@ -603,7 +603,7 @@
 {//entry_cnt is for preallocating dir blks.
   I64	c,cur_dir_clus=Name2DirClus(dv,cur_dir),
 	size=CeilU64((entry_cnt+3)<<6,BLK_SIZE);
-#assert CDIR_SIZE==64
+//#assert CDIR_SIZE==64
   U8 *buf=CAlloc(size);
   CDirEntry *d_native=buf-offset(CDirEntry.start);
   Bool unlock_break;

--- old/Kernel/KernelA.HH
+++ new/Kernel/KernelA.HH
@@ -2516,7 +2516,7 @@
 
 #help_index "File/Low Level;File/Program Routines"
 //CDirEntry flags (Used by $LK,"FileMgr",A="MN:FileMgr"$())
-#define CDIR_FILENAME_LEN	38 //Must include terminator zero
+#define CDIR_FILENAME_LEN	39 //Must include terminator zero
 public class CDirEntry
 {
   CDirEntry *next,*parent,*sub;